Census 2000 counted 281.4 million U.S. residents, of whom 12.5 percent were Hispanic. Mexicans represented 7.3 percent, Puerto Ricans 1.2 percent, Cubans 0.4 percent, and other Hispanics 3.6 percent of the population. Another 3.8 million Hispanics were counted in the Commonwealth of Puerto Rico. The Hispanic population increased by 57.9 percent since 1990. The concept and measurement of Hispanic origin have evolved across several censuses. Other Hispanic origins refer to various identifications. Salvadorans were the largest Central American group. More than three-quarters of Hispanics lived in the west or south. Half of all Hispanics lived in California and Texas. Counties with the highest proportion of Hispanics were along the southwestern U.S. border. Hispanics were present in some counties within nontraditional states. The Commonwealth of Puerto Rico was 98.8 percent Hispanic. In 2000, more than one million Hispanics lived in New York City and Los Angeles. Hispanics in East Los Angeles were 96.8 percent of the population. The Hispanic population in New Mexico is 42.1 percent of the total state population, the highest proportion for any state. The relative youthfulness of the Hispanic population was reflected in its population under age 18 years and its median age. Most, but not all, of the places with the largest specific Hispanic group populations were among the 10 places with the largest Hispanic populations. (SM)